1. Field of the Invention
The present invention relates to a video editing apparatus whereby a user can execute conversational-mode editing of a displayed picture which is generated from stored video data.
2. Description of the Related Art
With a prior art video editing apparatus, it is generally possible for the user to designate a region within a display picture produced by a display unit of the apparatus, and to then input a "cut-out" command to the video editing apparatus, whereby data corresponding to the designated region (such a region being referred to in the following as a cut-out region) are "cut-out" from the display picture, i.e. are replaced by predetermined other data. In the following, such other data will be referred to as the replacement data, for that cut-out region. It is possible that, after executing such an operation, the user may subsequently wish to move the cut-out data to another location in the display picture, or to re-insert the data which have been removed from a cut-out region. For that reason, in the prior art, the data which have been removed as a result of the cut-out operation (such data being referred to in the following as the cut-out region data) are stored, together with position information specifying the position of the cut-out region with respect to the display picture. Thus the user can thereafter control the video editing apparatus to either produce the display picture with the replacement data appearing in the cut-out region, or to read out the cut-out region data from memory and copy the cut-out region data into the appropriate position within a display memory area, to be displayed in its original position within the display picture. As used in the following, "display memory area" signifies a memory area whose contents are directly transferred to be displayed by a display unit, i.e. there is a direct correspondence between the stored data in the memory and the display contents, and the boundary of the memory area corresponds to the boundary of the display picture.
It will be assumed in the following that such cut-out regions are of rectangular shape, however other shapes are of course possible. In the case of a rectangular cut-out region, the position-specifying information which the user must input in order to designate a cut-out region data can for example consist of the coordinates of one corner of the region (e.g. the upper left-hand corner) and the height and width of the region. The user typically specifies each cut-out region by observing a cursor formed on the display, while using an input device such as a mouse and a keyboard to move the cursor.
However the following problems arise with such a prior art type of video editing apparatus. If display scrolling is executed after such a cut-out region data replacement/storage operation has been executed, then since the position of each cut-out region is defined with respect to the display picture prior to scrolling, that position information cannot be used to correctly locate each cut-out region in the new display picture. That problem is illustrated in FIG. 1, in which numeral 200 can be considered as representing a display picture produced by a display unit, or the contents of a display memory area whose contents are directly displayed by the display unit. Within the display picture 200, two cut-out regions designated as "a" and "b" have been formed, with replacement data for each of these appearing in the display picture (e.g. "all white" data values). If display scrolling in the downward direction is now executed, then the contents of the display picture will appear to be moved upward, as shown by display picture 201. However the two cut-out regions "a" and "b" will remain in the same positions on the screen (since their respective positions are fixedly specified with respect to boundaries of the display picture. Hence the cut-out regions will be in incorrect relative positions to the remainder of the display picture contents, after scrolling is performed, i.e. the cut-out regions have not been scrolled together with the remainder of the picture. Thus it will be necessary for the user to again designate position information for the cut-out regions and input "cut-out" commands, and the video editing apparatus then has to again write the replacement data into the corresponding positions in the display memory area.
Furthermore, after scrolling has been executed, it may be necessary to read out the replacement data from a storage medium such as a hard disk, to be copied into the appropriate new positions in the display memory area, to appear on the display at the correct position. However if there are a large number of cut-out regions formed, then a substantial amount of time is required for executing such operations, each time that display scrolling is executed. Thus, it has been difficult to achieve a sufficiently high speed of scrolling in such a case. This problem is especially severe in the case of applications in which it is necessary to have a capability for scrolling very rapidly, while being able to make sudden changes in the scrolling speed.
In FIG. 1, 202 denotes a display picture produced by enlargement of the display picture 200 (by the operation of a display enlargement/contraction section of a video editing apparatus, as described hereinafter). In this case too, the relative positions of the cut-out regions to the other contents of the display picture will be incorrect, after the display enlargement processing, while in addition the sizes of the cut-out regions will be incorrect.
Another problem of prior art types of video editing apparatus will be described referring to the data flow diagram of FIG. 2 and processing flow diagram of FIG. 3. In FIG. 2, 401 denotes a display picture produced by a display unit. Numeral 402 denotes a display memory area whose contents correspond directly to the contents of the display picture. 403 denotes an original data memory area, whose contents can be changed by display editing commands generated by the user. A selected data region 406 within the original picture data memory area 403 is copied into the display data memory area 402. Numeral 404 denotes a memory area referred to as an "UNDO" memory area, whose function will be described in the following and which is equal in size to the original picture data memory area 403. 407 denotes a region within the display picture 401 which it will be assumed that the user is to change by display editing, from the previous contents consisting of a vertical "stick figure", to a horizontal figure as indicated, i.e. by rotation of the region 401 by 180.degree.. The operation will be described referring to FIG. 3. In step ST1, the user is performing various display processing operations, such as commands for moving a cursor or for executing display editing, by operating a mouse and keyboard for example. If it is detected in step ST2 that an editing processing command (or an "undo" command as described in the following) has been supplied, then the contents of the command are temporarily set into a register (step ST2), then in step ST4 a decision is made as to whether or not the command held in the register is an "undo" command, i.e. a command which specifies that the effects of the most recent editing processing command are to be eliminated. If it is found that the command is not an "undo" command but is a display editing processing command, then in step ST5 the entire contents of the original picture data memory area 403 are copied into the UNDO memory area 404. The display editing processing command contents are then read out from the register (step ST6), and are applied to the contents of the original picture data memory area 403, i.e. within the selected data region 406 in the original picture data memory area 403. Thus for example the contents of the region 408 are changed as shown from data representing the vertical stick figure to data representing the horizontal stick figure. The contents of the selected data region 406 in the memory area 403 are then copied into the display data memory area 402 (step ST7) so that the results of the editing processing will now appear on the display picture 401, i.e. the vertical stick figure in the region 407 of the display picture will be changed to a horizontal figure.
If however it is found in step ST4 that an "undo" command has been supplied, then the entire contents of the UNDO memory area 404 are copied into the original picture data memory area 403 (step ST6). Step ST7 is then executed, and as a result, the effects of the most recent display editing processing command will be eliminated from the display picture 401.
However such a system has two basic disadvantages. Firstly, when the user inputs a display editing processing command, then the system first has to copy the entire contents of the original picture data memory area 403 into the UNDO memory area 404, then perform the editing processing calculations and accordingly alter the contents of the original picture data memory area 403, then copy the selected data region from the original picture data memory area 403 into the display data memory area 402, to be transferred to the display unit and displayed. Thus, a substantial amount of time is required between the inputting of a display editing processing command and the appearance of the resultant display picture, i.e. there is a slow response to a display editing input operation that is executed by the user.
Secondly, since the memory capacity of the UNDO memory area 404 must be the same as that of the original picture data memory area 403, the overall amount of memory capacity required in the system is excessive. For example, assuming that the display size corresponds to an A3 size document sheet, and that the picture element density is 200 DPI (dots per inch), then a total memory capacity of approximately 4 megabytes will be necessary.